The present invention relates to an electrochemical composite storage system comprising a plurality of electrochemical storage modules. The present invention particularly relates to an electrochemical composite storage system which is designed to operate a plurality of strings of storage modules, which strings are connected in parallel, without unequal states of charge or undesired compensation currents occurring.
Electrochemical storage modules with a simple half- or full-bridge as the coupling unit are known from the prior art. Modules of this kind can be used to set the terminal voltage of a respective module in certain limits. However, current regulation is not possible with units of this kind. A storage module which is called a UniBB (Universal Buck-Boost) module is also known from the prior art, said module comprising one or more rechargeable battery cells together with a coupling unit, wherein the coupling unit also contains an inductance. This module can be used both as a voltage source and as a current source. Since a module of this kind is designed for voltages of below 60 V, it is necessary, in particular for applications which have extremely large power requirements (for example vehicles in the automobile industry), for a plurality of modules to be connected in series in order to reach the available power at a controllable current. In addition, it may be necessary to connect these serial strings in parallel with one another in order to further increase the available current. However, in the normal case according to the prior art, connecting strings in parallel leads to undesired compensation currents between the strings on account of generally unequal states of charge. A possible design of a UniBB module is discussed in greater detail further below in conjunction with FIG. 4.
One object of the present invention is to provide an electrochemical energy store which is of modular construction and remedies the disadvantages of the prior art.